text: from django.core.validators import BaseValidator
  from django.utils.translation import ugettext_lazy as _
  
  class MinListLengthValidator(BaseValidator):
      compare = lambda self, a, b: a < b
      clean   = lambda self, x: len(x)
      message = _(u'Ensure this list has at least %(limit_value)d items (it has %(show_value)d).')
      code = 'min_length'
      
      
      
  class MaxListLengthValidator(BaseValidator):
      compare = lambda self, a, b: a > b
      clean   = lambda self, x: len(x)
      message = _(u'Ensure this list has at most %(limit_value)d items (it has %(show_value)d).')
      code = 'max_length'    